If The Weather Channel can be believed -- and since we're not asking them for the forecast, let's assume so -- if the air temperature is 90º F, it will be up to 124º F inside your car in 30 minutes. We all know enough not to leave our children or dogs in a car on a steamy day like that, but this column is about other babies that also do poorly in such heat: bottles of wine. It's easy if you're out visiting wine country to buy a few here, then a few at the next stop, then stop for a picnic lunch.... In the meantime those recently purchased prizes that tasted so good in that cave setting or thanks to the flirty pourer's charm at the tasting room is turning on you before you even get home.
What to do? Either pack a cooler with ice, or, as Kayla Bonnin, Marketing Manager, at Santa Barbara's Carr Winery advises, "Don't leave wine in the car, take it inside with you." After all, those people at your next stop are in the business, and will completely understand what you're doing (as long as you don't open a competitor's bottle on site, of course). The last thing you'd want to do is kill something as special, for example, as an aged pinot gris from Carr -- and they have ones going on a decade old that are just gaining in complexity (who knew?).
So what do I mean by "kill"? A cooked bottle doesn't taste so bad that you'll need to spit it out, unless the wine had some other defect. But it will seem less fresh, and if it's been subject to heat long enough, might even taste a bit stewy, as if its fruit had been left to simmer on a stove. As you no doubt remember from high school physics, heat makes the wine, which is mostly water, after all, expand; that expansion can either force some wine out around the cork--look for those tell-tale leaks if you have any concern about heat damage--and in some cases even push the cork some. This makes it possible for more air to get back into the bottle, too, so unless you live in a clean room, that air might be bringing nasty microbes you don't want in your wine.
There really isn't a rescue you perform at this point. It is better to drink a heat-affected wine sooner than later, as it's only going to get worse over time thanks to that air transfer issue. And there's always the sink if a bit of boiled prune isn't what you'd hoped for in your classic cabernet.
Also remember that drastic temperature changes can also be bad for your wine (yes, it's good for grapes on the vine, but that's a different story). That's why you don't drink the wine at your friend's house with the wine storage above the Wolf stove, no matter how stunning the redesign looks. Wine likes consistency, as much as possible. Not to mention the dark, as light also pushes the heat issue. Think of it this way: wine likes its mood lighting as much as you might like it when drinking it.